toji/gl-matrix — pull request #22 by abberg (2012-04-10 17:36:14+00:00)
Title: Added .add and .scale methods to quat4

Used for the addition of two quaternions and the multiplication of a quaternion by a scalar, useful for rotating quaternion by an angular velocity vector. see http://www.gamedev.net/topic/510087-rotating-quaternions-using-angular-velocity/